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Old 29th September 2009, 12:54 PM   #1
djn04 is offline djn04  United States
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Default Hi(ish) end Simple SE

I made a pair of Zaph Audio ZRT's with scan speak drivers and I'm looking to make an amp of equal quality. The simple SE seems like something I can handle.

My initial thoughts are to go with some KT88 and James OPT. Are there other OPT out there that I should consider? Elctra-Print, Tamura, etc.

Also what about power transformer and choke? Are there brands to look at that would mate well with KT88's and James OPT.

Lastly would upgrading the caps or resistors make a performance difference? Something like Black Gate.

This forum has been a wealth of information and I'm looking forward to starting this project.
Thanks
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Old 29th September 2009, 01:52 PM   #2
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For high end try Hashimoto, they have all the iron, power, choke, output. Try Vcap TFTF for coupling. For bypass caps, try Elna similic II.

http://www.tube-amps.net/Hashimoto_Products.htm
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Old 29th September 2009, 02:09 PM   #3
n_maher is offline n_maher  United States
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Quote:
Originally Posted by djn04 View Post
I made a pair of Zaph Audio ZRT's with scan speak drivers and I'm looking to make an amp of equal quality. The simple SE seems like something I can handle.

My initial thoughts are to go with some KT88 and James OPT. Are there other OPT out there that I should consider? Elctra-Print, Tamura, etc.
[shill mode]If you wanted to save yourself time and a good chunk of change you could just look here...
http://www.diyaudio.com/forums/swap-meet/138436-complete-simplese-tube-speaker-amp-diy.html#post1742758
[/shill]
Of course half the fun is building it, right? The trafo recommendations made so far are good ones, I'd toss Sowter into the mix as well. There's no shortage of choices but sourcing them, lead times, and shipping can and will play a role for sure. I'd also suggest that you take care with the power supply aspect, I think it matters every bit as much as the output iron that you use. There's a myriad of choices for passive components as well, I'm a Holco guy mostly for tube gear and that's worked well for me so far.
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Old 29th September 2009, 02:16 PM   #4
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For KT88 in the Simple SE, I'd expect about 450 volt B+ supply. Use a 510 ohm cathode resistor, and I'd recommend an output transformer designed for 3.5K~5K loading on the primary. Be sure to consider the nominal impedance of your speakers, and confirm the transformer you select has a compatible secondary winding. Take a look at George's transformer page.

If "high end" is your design criteria, I expect there will be recommendations for transformers from Hasimoto, Sophia Electric, Lundahl, and Silk. You could probably do well with transformers from James, Electra-Print or Magnequest as well.

I've started a Wiki page with contact information for various transformer suppliers. Please take a look at it if you get the chance.
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Old 29th September 2009, 05:09 PM   #5
djn04 is offline djn04  United States
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Quote:
Originally Posted by n_maher View Post
[shill mode]If you wanted to save yourself time and a good chunk of change you could just look here...
http://www.diyaudio.com/forums/showthread.php?p=1742758
[/shill]
That is a great price but building it is most of the fun. I guess I could take it apart and put it back together again.
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Old 29th September 2009, 05:59 PM   #6
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This is if it was my build, I have contemplated a build such as this before for either a Simple SE or Tubelab SE.

-Electra-Print Iron all the way around or Magnequest. Magnequest power iron can be a bit hard to come by unless you watch their forum or beg it out of Mike.
-Film capacitors on the power supply side, either Solen PPE or (preferable) ASC Oil.
-Mundorf Supreme Silver and Oil coupling capacitors (or I suppose V-Caps).
-For resistors I would use PRP's most ½watt places, Riken's for grid stoppers, and Kiwame's everywhere else except the output tubes cathode, this would be a Mills MRA.

On the Simple SE I would change a few things if I where doing it:
1. I would change the front end to use LED bias, eliminating the resistor and cathode bypass capacitor.
2. I would add a small daughter board with a cascode DN2540 current source instead of the 10M45. This would offer a few advantage, at least on paper:
- It would give an increase in load impedance over the entire frequency band compared to the 10M45.
- It has significantly lower shunt capacitance compared to the 10M45.
- It would allow you to use the "mu-follower" output on the ccs offering a much lower impedance and more drive to the grid of the output tubes. This may or may not matter in the end, as the 12AT7 can probably drive the EL34/6L6/KT88 just fine, but an option.
3. I would re-size the output tubes cathode bypass capacitor, with a KT88/6550, something in the neighborhood of 330uF with a 510R cathode resistor. This would allow you to use a high quality capacitor without selling a kidney. You could try too replacing the whole R-C with a current source, all up to you. At 330uF your -3 point should be at about 10Hz, which should be below the roll off of the output transformer.
4. I would solder everything to the PCB, no terminal blocks. Also I would jumper triode connection and no cathode feedback right at the PCB. This is just me, but I trust a good solder joint over a terminal block just about any day... maybe just old school. It isn't a huge issue though, it is nice to be able to easily remove things and switch things in and out. I wouldn't use a standby switch I don't think if I was just using the 5AR4, but you still might want to include it. Just another way to extent tube life.
5. Personally I would drop the volume pot and use a line amplifier. Though I don't know why since I am working (slowly) on a Musical Machine which is integrated. Something to me just feels right about dropping the pot on this amplifier, but it is nice to get one more active component out of the signal path. If I did this I think I would look to a 12B4A (maybe choke loaded, sitting atop a CCS...maybe), or a 6SN7 actively loaded, common cathode/cathode follower, think Extended Foreplay or VTV with CCS's. Lastly, maybe a Electra-Print Ultrapath line amplifier, all film caps, with 2 x 2C22's.

I would use EL34's but that is just me. Either way I would look for good quality NOS tubes. 12AT7's are fairly cheap to come by as NOS, 5AR4's are a bit pricier, KT88's or real Tung-Sol 6550's will set you back a bit. I would go through and if it isn't much trouble, put a resistor inline with one of the heater wires from the transformer to the pcb. Size it to drop the heater voltage to around 6.2v or so. You shouldn't hear the difference. This, along with an operating point within the limits of the tubes, and you will get nice long happy lives out of NOS tubes. In some cases many times longer than new production tubes from China or Russia.

Maybe a bit much, but you asked, hehe.
Cheers and happy listening!
James

Last edited by JPeitzman; 29th September 2009 at 06:04 PM.
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Old 29th September 2009, 06:07 PM   #7
djn04 is offline djn04  United States
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James-
My head is spinning. I feel like I should compensate you for that reply I'll have to digest it and I'm sure I'll have more questions. I can see this project sucking a serious amount of time in the planning stages. I still have a lot to learn.
Thanks
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Old 29th September 2009, 06:11 PM   #8
ChrisA is offline ChrisA  United States
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Originally Posted by djn04 View Post
...
Also what about power transformer and choke? Are there brands to look at that would mate well with KT88's and James OPT.

Lastly would upgrading the caps or resistors make a performance difference? Something like Black Gate....
Do you plan on using solid state diodes or a tube rectifier? You have to decide this before you can select a power transformer. I'd go solid state because I think you can get a "stiffer" and more solid power supply but many people just like the idea of all tubes. If you go with a tube your first filter cap is constrained to about 50 or 100 uF by the tube's data sheet. SS diodes can handle much higher in-rush current.

I don't think a power transformer can color the sound. It can "bottle neck" the sound if undersized. I think you get the best deal by going with a plain old, built-like-a-tank Hammond 300 series PT but buying one rated about 150% of the required current.

Chokes are the same way, If you have a budget of X dollars you can buy either a bigger Hammond or a smaller boutique brand. Go with the one that has the greater weight and higher current rating.
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Old 29th September 2009, 06:12 PM   #9
djn04 is offline djn04  United States
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Originally Posted by Ty_Bower View Post
I've started a Wiki page with contact information for various transformer suppliers. Please take a look at it if you get the chance.
This is exactly what I've been looking for. This gives me an idea of the relative expense of each.
Thanks
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Old 29th September 2009, 06:15 PM   #10
djn04 is offline djn04  United States
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Originally Posted by ChrisA View Post
Do you plan on using solid state diodes or a tube rectifier? You have to decide this before you can select a power transformer.
Frankly I'm still in the learning stages and I don't know the pros/cons of tube vs. solid state. My gut tells me I'd like to go with tubes but I don't know at this point.
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